september, 2022

29sep11:0012:00Industry presentations11:00 - 12:00(GMT+02:00) View in my time


    • 29. september 2022
    • 11:00 Acciaierie Bertoli Safau Centre - ABSBAIN Steels: New Comers in the Wide Bainitic and Micro-Alloyed Steels Family. Case Study of Applicability of Quenching and Partitioning on Hot Forged Components11:00 - 11:30Christophe Stocky - Acciaierie Bertoli Safau Centre

      For half a century, so-called bainitic structure steels have been developed in order to offer an alternative to micro-alloyed forging steels. In both cases, the objective is the same: to replace quenched and tempered steels which are more expensive and energy-consuming. Quenching and tempering is also an additional source of greenhouse gas (GHG). If bainitic steels are presented as an interesting alternative, they present, like ferrite perlite micro-alloyed steels, for some characteristics lower values than quenched and tempered steels. Until now, for hot forged components, the use of solutions without heat treatment was synonymous with “controlled” cooling (“natural” cooling in calm air, forced air or even cooling followed by isothermal holding after forging). But in comparison to quenched and tempered martensitic solutions, the limit of use of this type of structure obtained by natural cooling is often expressed during a Charpy-type impact test. However, in parallel with these difficulties, the reduction of GHGs is becoming more and more essential and the increase in mechanical characteristics remains a relevant strategy that would allow aditional downsizing of the forged components and it should be reconsidered in regards to the fatigue behavior which is similar to quenched tempered steels. For twenty years, several authors have demonstrated the virtues of a quenching and partitioning treatment (subsequently called QP) which makes it possible to obtain a mixed structure with a less brittle martensite and a fine bainitic structure with a morphology favoring ductility properties. Besides a review of market solutions, presentation of our solutions, we will discuss the applicability of an eventual in-line QP treatment for forged components.


      Variety in engineering applications with continuously increasing performance demand forces producers to develop novel and/or improved material solutions. In addition to these challenging material property expectations, worldwide energy crisis and greenhouse gas reduction requirements pushes producers to optimize their processes simultaneously. Both material and process development require a simulation supported methodology which should be started from pilot scale and extended to industrial scale. At Asil Çelik, in addition to continuous casting, ingot casting is being used to produce various steel grades, especially special grades such as tool steels, which can also be further refined by Electroslag Remelting (ESR) and then thermomechanically shaped by either rolling or open die forging. Consequently, a wide variety of ingots in terms of size and geometry are being produced at Asil Çelik, which makes ingot mold design and process parameter optimization efforts compulsory. Moreover, research and development activities are also focusing towards modification of special steel grades along with novel alloy design for improved material performance and reduced cost. In this talk, first results of simulation supported ingot casting optimization studies will be discussed. Next, in the scope of material development activities, results of two case studies comprising of chemical composition modification of a hot work tool steel grade and design of a novel low carbon bainitic (LCB) steel will be presented.